Refrigeration systems that operate with a refrigerant fluid having carbon, such as CO2 in its composition, present operational pressures higher than those obtained with other refrigerant fluids, requiring stronger compressors.
In some of said constructions, the cylinder block defines part of the compressor shell in which the motor-compressor assembly and the compression system of the compressor are mounted. The cylinder block defines, therewithin, a compression cylinder housing a piston which reciprocates, in suction and discharge strokes of the refrigerant gas from and to a refrigeration system to which the compressor is coupled. The compression cylinder is closed, at one end, by a valve plate onto which is mounted a head usually defining at least one of the discharge and suction chambers of the compressor. In the known constructions, a shell portion incorporating the cylinder block is hermetically closed by one or two outer end covers, one of them usually defining an oil reservoir therewithin.
In some of these constructions, the head affixed to the cylinder block is provided externally to the contour of the shell portion of the compressor, being affixed to the cylinder block by means of screws (WO2005/026548) or by welding.
The systems for affixing the head to the cylinder block by means of screws can present, over time, undesirable leaks of the refrigerant fluid in the form of gas. Since the head, in these constructions, is external to the contour of the shell portion, the refrigerant gas leaks to the environment in which the compressor is installed, resulting in volume loss of said gas in the refrigeration system.
Besides the possibility of gas leak, the known compressor constructions in which the head is external to the shell contour present an undesirable noise level. The construction in which the head is externally provided has the advantage of allowing a better dissipation of the heat generated by the gas compression in the discharge operation of the compressor. However, such known constructions still allow the heating of the internal parts of the compressor, due to the heat that is transferred from the head to the compressor parts provided adjacent to said head.